Computational study of elliptic subsonic jet controlled by air tabs

Purpose This paper aims to present the mixing and decay characteristics of Mach 0.8 elliptic jet manipulated by air tabs, through numerical simulation. Design/methodology/approach The Air Tabs are secondary jets injected through two 1-mm diameter tubes, which are placed at the exit plane of the elliptic primary nozzle. Two air tab configurations are considered for the present study; in the first case, they are placed along the major axis, and in the second case along the minor axis of the elliptic nozzle exit. The air tab Mach numbers considered are 0.8, 0.9 and 1.0. The numerical simulations have been performed in ANSYS-CFX software using the k-e turbulence model. Findings The jet centerline (X) total pressure decay reveals that air tabs placed along the minor axis promote jet mixing more efficiently than those placed along the major axis. It is also observed that the air tabs along the minor axis provoke the jet to split into two parts thus resulting in faster spread in the perpendicular direction (Z). When compared against the uncontrolled jet, air tabs at Mach 1.0 placed along the minor axis produce 80% reduction in the potential core, whereas that along the major axis brings down the axis-switching location to 0.95 Deq from 3.7 Deq. Practical implications In aerospace applications, enhancing the mixing between fuel and air would result in better combustion efficiency, faster exhaust jet mixing with ambient, which in turn result in reduced jet acoustics as well as infrared signature, thereby promotes environmental sustainability. Originality/value To the best of the authors’ knowledge, there has not been a thorough analysis of the effects of air tabs on the mixing and decay characteristics of elliptic Mach 0.8 jet.